# Sub Applications - Mounts

If you need to have two independent FastAPI applications, with their own independent OpenAPI and their own docs UIs, you can have a main app and "mount" one (or more) sub-application(s).

## Mounting a **FastAPI** application

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

        }

        in 5..7 -> {
          data.writeByte('\n'.code) // 'data' on a line of its own.
        }

        in 8..9 -> {
          id = source.readUtf8LineStrict().takeIf { it.isNotEmpty() }
        }

        in 10..12 -> {
          id = null // 'id' on a line of its own.
        }

        in 13..14 -> {
          type = source.readUtf8LineStrict().takeIf { it.isNotEmpty() }
        }

* If a socket is found, istio-agent will not start its own SDS Server and Envoy will be configured to use that socket as its source of cryptographic material.

            define its own format and semantics. This was generally a properties format.
            <p>Since Maven 3.2.4, the type for this field has been changed to Properties to match the de-facto
            format.
            <p>Each toolchain defines its own properties names and semantics.
          </description>
        </field>
        <field>

# The preview profile contains features that are experimental.
# This is intended to explore new features coming to Istio.
# Stability, security, and performance are not guaranteed - use at your own risk.
apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
spec:
  values:

So, even with the code above that doesn't use Pydantic explicitly, FastAPI is using Pydantic to convert those standard dataclasses to Pydantic's own flavor of dataclasses.

And of course, it supports the same:

* data validation
* data serialization
* data documentation, etc.

# The preview profile contains features that are experimental.
# This is intended to explore new features coming to Istio.
# Stability, security, and performance are not guaranteed - use at your own risk.
meshConfig:
  defaultConfig:
    proxyMetadata:
      # Enable Istio agent to handle DNS requests for known hosts
      # Unknown hosts will automatically be resolved using upstream dns servers in resolv.conf

# The preview profile contains features that are experimental.
# This is intended to explore new features coming to Istio.
# Stability, security, and performance are not guaranteed - use at your own risk.
meshConfig:
  defaultConfig:
    proxyMetadata:
      # Enable Istio agent to handle DNS requests for known hosts
      # Unknown hosts will automatically be resolved using upstream dns servers in resolv.conf

# The preview profile contains features that are experimental.
# This is intended to explore new features coming to Istio.
# Stability, security, and performance are not guaranteed - use at your own risk.
meshConfig:
  defaultConfig:
    proxyMetadata:
      # Enable Istio agent to handle DNS requests for known hosts
      # Unknown hosts will automatically be resolved using upstream dns servers in resolv.conf

# The preview profile contains features that are experimental.
# This is intended to explore new features coming to Istio.
# Stability, security, and performance are not guaranteed - use at your own risk.
meshConfig:
  defaultConfig:
    proxyMetadata:
      # Enable Istio agent to handle DNS requests for known hosts
      # Unknown hosts will automatically be resolved using upstream dns servers in resolv.conf